In the last 40 years, Coleman’s findings, known informally as the Coleman Report, have been confirmed again and again. Most recently, in a 2006 study, Douglas Harris, an economist at the University of Wisconsin, found that when more than half the students were low-income, only 1.1 percent of schools consistently performed at a “high” level (defined as two years of scores in the top third of the U.S. Department of Education’s national achievement database in two grades and in two subjects: English and math). By contrast, 24.2 percent of schools that are majority middle-class met Harris’s standard.

There are, of course, determined urban educators who have proved that select schools filled with poor and minority students can thrive — in the right circumstances, with the right teachers and programs. But consistently good education at schools with such student bodies remains the rare exception. The powerful effect of the socioeconomic makeup of a student body on academic achievement has become “one of the most consistent findings in research on education,” Gary Orfield, a U.C.L.A. education professor, and Susan Eaton, a research director at Harvard Law, wrote in their 1996 book, “Dismantling Desegregation.”

Most researchers think that this result is brought about by the advantages that middle-class students bring with them. Richard Kahlenberg of the Century Foundation lays them out in his 2001 book, “All Together Now”: more high-level classes, more parent volunteers and peers who on average have twice the vocabulary and half the behavioral problems of poor students. And, especially, more good teachers. Harris, the economist, says that poor minority students still don’t have comparable access to effective teachers, measured by preparation and experience. The question, then, is whether a plan that integrates a district by class as well as by race will help win for all its schools the kind of teaching that tends to be linked to achievement. “The evidence indicates that it would,” Harris says.

Ronald Ferguson, an economist at the Kennedy School of Government at Harvard, is less persuaded. His research highlights the nagging persistence of a racial achievement gap in well-off suburbs. “What happens with the achievement gap in a place like Louisville,” he says, “will depend on how vigilant their leaders are to make sure high-quality instruction is delivered across the board.” Such teaching is more likely in a school with a critical mass of middle-class parents, he concedes. But he stresses that to reap the benefits, poor kids have to be evenly distributed among classrooms and not just grouped together in the lowest tracks. “To the degree a district takes the kids who struggle the most academically and spreads them across different classrooms, they’re making teachers’ work more doable,” he says. “And that may be the biggest effect.”

Whatever the exact answer, there is some support for the view that schools can handle a substantial fraction of poor students without sacrificing performance. In Wake County, test scores of middle-class students have risen since instituting income-based integration. Additionally, Kahlenberg points out that middle-class students are generally less influenced by a school’s environment because they tend to learn more at home, and that the achievement of white students has not declined in specific schools that experienced racial (and thus some class) desegregation.

Would schools need to track students by ability to protect middle-class students, who are more often higher-achieving than their low-income peers? Perhaps not. In a 2006 longitudinal study of an accelerated middle-school math program in Nassau County N.Y., which grouped students heterogeneously, the authors found that students at all achievement levels, as well as minority and low-income students, were more likely than the students in tracked classes to take advanced math in high school. In addition, the kids who came into the program as math whizzes performed as well as other top-achievers in homogenous classes.

This study underscores Ronald Ferguson’s point about the value of seating students of different backgrounds and abilities in class together, as opposed to tracking them. Still, it’s worth noting that less than 15 percent of the students studied in Nassau County were low-income. So the math study doesn’t tell us what happens to the high-achieving middle-class kids when close to half of their classmates aren’t as well off.

I’ve posted about the missed opportunities for Madison to be a leader in this new integration movements many times. Two examples are linked below. I do want to make clear — as I wrote in one of those posts — I believe that “[f]or the most part MMSD has done a very good, if relatively quiet and indirect job of addressing [all kinds of] diversity. ” I’m still asking for more.

Was curious about this one paragraph and wondered if you could give us some more background, perhaps as an update, if warranted.

“Todd and her planners wanted to tackle the problem, she says, but they were mindful of going too far in their efforts and losing the support of parents. In other districts — including Cincinnati, Evanston, Ill., Bibb County, Ga., and Madison, Wis. — the reaction to the Supreme Court’s ruling had been to move to dismantle racial-integration programs. Todd and other school officials didn’t want integration redefined to turn into no integration all. To get a handle on a new plan, Todd turned to an heir of James Coleman: the researcher John Powell.”

The Madison practices should survive a legal challenge; they appear to be within the limits Justice Kennedy laid out (with the exception of the State inter-district transfer stuff…Madison followed the law, but that is gone now).

Evanston is the case I know best. In their k-8 schools for years they have followed a 60% guideline, with the rule that no school can have more than 60% of any racially identifiable group. This has resulted in much busing and controversy over the years (some about the idea of busing for integration, some about who is bused and who gets a neighborhood school). I am not sure the current status.